vulkan: use fewer FA rows for small cache runs (#18280)

ggml/src/ggml-vulkan/ggml-vulkan.cpp

@@ -379,18 +379,18 @@ enum FaCodePath {
 };
 
 struct vk_fa_pipeline_state {
-    vk_fa_pipeline_state(uint32_t HSK, uint32_t HSV, bool small_rows, FaCodePath path, bool aligned, bool f32acc)
-        : HSK(HSK), HSV(HSV), small_rows(small_rows), path(path), aligned(aligned), f32acc(f32acc) {}
+    vk_fa_pipeline_state(uint32_t HSK, uint32_t HSV, bool small_rows, bool small_cache, FaCodePath path, bool aligned, bool f32acc)
+        : HSK(HSK), HSV(HSV), small_rows(small_rows), small_cache(small_cache), path(path), aligned(aligned), f32acc(f32acc) {}
 
     uint32_t HSK, HSV;
-    bool small_rows;
+    bool small_rows, small_cache;
     FaCodePath path;
     bool aligned;
     bool f32acc;
 
     bool operator<(const vk_fa_pipeline_state &b) const {
-        return std::tie(HSK, HSV, small_rows, path, aligned, f32acc) <
-               std::tie(b.HSK, b.HSV, b.small_rows, b.path, b.aligned, b.f32acc);
+        return std::tie(HSK, HSV, small_rows, small_cache, path, aligned, f32acc) <
+               std::tie(b.HSK, b.HSV, b.small_rows, b.small_cache, b.path, b.aligned, b.f32acc);
     }
 };
 
@@ -2582,10 +2582,10 @@ static void ggml_vk_wait_events(vk_context& ctx, std::vector<vk::Event>&& events
 static constexpr uint32_t flash_attention_num_small_rows = 32;
 static constexpr uint32_t scalar_flash_attention_num_small_rows = 1;
 
-static uint32_t get_fa_scalar_num_large_rows(uint32_t hsk, uint32_t hsv) {
+static uint32_t get_fa_scalar_num_large_rows(uint32_t hsk, uint32_t hsv, bool small_cache) {
     if (hsv >= 192) {
         return 2;
-    } else if ((hsv | hsk) & 8) {
+    } else if ((hsv | hsk) & 8 || small_cache) {
         return 4;
     } else {
         return 8;
@@ -2607,9 +2607,8 @@ static uint32_t get_fa_num_small_rows(FaCodePath path) {
     }
 }
 
-static std::array<uint32_t, 2> fa_rows_cols(FaCodePath path, uint32_t hsk, uint32_t hsv, uint32_t clamp, ggml_type type, bool small_rows) {
+static std::array<uint32_t, 2> fa_rows_cols(FaCodePath path, uint32_t hsk, uint32_t hsv, uint32_t clamp, ggml_type type, bool small_rows, bool small_cache) {
     GGML_UNUSED(clamp);
-    GGML_UNUSED(hsv);
 
     if (path == FA_SCALAR) {
         if (small_rows) {
@@ -2618,9 +2617,9 @@ static std::array<uint32_t, 2> fa_rows_cols(FaCodePath path, uint32_t hsk, uint3
             if ((hsv | hsk) & 8) {
                 // HSV/HSK not being a multiple of 16 makes D_split smaller, which makes cols_per_iter
                 // larger, and Bc needs to be >= cols_per_thread. 64 is large enough, 32 is not.
-                return {get_fa_scalar_num_large_rows(hsk, hsv), 64};
+                return {get_fa_scalar_num_large_rows(hsk, hsv, small_cache), 64};
             } else {
-                return {get_fa_scalar_num_large_rows(hsk, hsv), 32};
+                return {get_fa_scalar_num_large_rows(hsk, hsv, small_cache), 32};
             }
         }
     }
@@ -2649,8 +2648,8 @@ static std::array<uint32_t, 2> fa_rows_cols(FaCodePath path, uint32_t hsk, uint3
     return {64, 64};
 }
 
-static uint32_t fa_align(FaCodePath path, uint32_t hsk, uint32_t hsv, ggml_type type, bool small_rows) {
-    return fa_rows_cols(path, hsk, hsv, 0, type, small_rows)[1];
+static uint32_t fa_align(FaCodePath path, uint32_t hsk, uint32_t hsv, ggml_type type, bool small_rows, bool small_cache) {
+    return fa_rows_cols(path, hsk, hsv, 0, type, small_rows, small_cache)[1];
 }
 
 static bool ggml_vk_matmul_shmem_support(const vk_device& device, const std::vector<uint32_t>& warptile, bool mul_mat_id, ggml_type src0_type) {
@@ -2992,11 +2991,11 @@ static void ggml_vk_load_shaders(vk_device& device) {
                                        align, disable_robustness, require_full_subgroups, required_subgroup_size);
     };
 
-    auto const &fa_wg_denoms = [&](FaCodePath path, uint32_t hsk, uint32_t hsv, uint32_t clamp, ggml_type type, bool small_rows) -> std::array<uint32_t, 3> {
-        return {fa_rows_cols(path, hsk, hsv, clamp, type, small_rows)[0], 1, 1};
+    auto const &fa_wg_denoms = [&](FaCodePath path, uint32_t hsk, uint32_t hsv, uint32_t clamp, ggml_type type, bool small_rows, bool small_cache) -> std::array<uint32_t, 3> {
+        return {fa_rows_cols(path, hsk, hsv, clamp, type, small_rows, small_cache)[0], 1, 1};
     };
 
-    auto const &fa_spec_constants = [&](FaCodePath path, uint32_t hsk, uint32_t hsv, uint32_t clamp, ggml_type type, bool small_rows) -> std::vector<uint32_t> {
+    auto const &fa_spec_constants = [&](FaCodePath path, uint32_t hsk, uint32_t hsv, uint32_t clamp, ggml_type type, bool small_rows, bool small_cache) -> std::vector<uint32_t> {
         // For large number of rows, 128 invocations seems to work best.
         // For small number of rows (e.g. N==1), 256 works better. But matrix granularity for 256 is 32, so we
         // can't use 256 for D==80.
@@ -3006,7 +3005,7 @@ static void ggml_vk_load_shaders(vk_device& device) {
         uint32_t wg_size = (path == FA_SCALAR || path == FA_COOPMAT1)
                             ? scalar_flash_attention_workgroup_size
                             : ((small_rows && (D % 32) == 0) ? 256 : 128);
-        auto rows_cols = fa_rows_cols(path, hsk, hsv, clamp, type, small_rows);
+        auto rows_cols = fa_rows_cols(path, hsk, hsv, clamp, type, small_rows, small_cache);
 
         // D_split can't be larger than a subgroup because we use subgroupShuffle to reduce it.
         // D_split can't be larger than the LSB of D divided by 4 due to vectorization in the shader.
@@ -3021,21 +3020,22 @@ static void ggml_vk_load_shaders(vk_device& device) {
             uint32_t HSK = fa.first.HSK; \
             uint32_t HSV = fa.first.HSV; \
             bool small_rows = fa.first.small_rows; \
+            bool small_cache = fa.first.small_cache; \
             FaCodePath path = fa.first.path; \
             bool aligned = fa.first.aligned; \
             bool f32acc = fa.first.f32acc; \
             if (path == FAPATH) { \
                 if (aligned) { \
                     if (f32acc) { \
-                        ggml_vk_create_pipeline(device, fa.second, "flash_attn_f32_f16_aligned_f32acc" #NAMELC, flash_attn_f32_f16_ ## NAMELC ##            SUFFIX ## _len,  flash_attn_f32_f16_ ## NAMELC ##            SUFFIX ## _data,  "main", 6, sizeof(vk_flash_attn_push_constants), fa_wg_denoms(FAPATH, HSK,HSV,0,TYPE,small_rows), fa_spec_constants(FAPATH, HSK,HSV,0,TYPE,small_rows), fa_align(FAPATH,HSK,HSV,TYPE,small_rows), true, true, (FAPATH==FA_COOPMAT1 ? 32 : 0));     \
+                        ggml_vk_create_pipeline(device, fa.second, "flash_attn_f32_f16_aligned_f32acc" #NAMELC, flash_attn_f32_f16_ ## NAMELC ##            SUFFIX ## _len,  flash_attn_f32_f16_ ## NAMELC ##            SUFFIX ## _data,  "main", 6, sizeof(vk_flash_attn_push_constants), fa_wg_denoms(FAPATH, HSK,HSV,0,TYPE,small_rows,small_cache), fa_spec_constants(FAPATH, HSK,HSV,0,TYPE,small_rows,small_cache), fa_align(FAPATH,HSK,HSV,TYPE,small_rows,small_cache), true, true, (FAPATH==FA_COOPMAT1 ? 32 : 0));     \
                     } else { \
-                        ggml_vk_create_pipeline(device, fa.second, "flash_attn_f32_f16_aligned_f16acc" #NAMELC, flash_attn_f32_f16_ ## NAMELC ## _f16acc ## SUFFIX ## _len,  flash_attn_f32_f16_ ## NAMELC ## _f16acc ## SUFFIX ## _data,  "main", 6, sizeof(vk_flash_attn_push_constants), fa_wg_denoms(FAPATH, HSK,HSV,0,TYPE,small_rows), fa_spec_constants(FAPATH, HSK,HSV,0,TYPE,small_rows), fa_align(FAPATH,HSK,HSV,TYPE,small_rows), true, true, (FAPATH==FA_COOPMAT1 ? 32 : 0));     \
+                        ggml_vk_create_pipeline(device, fa.second, "flash_attn_f32_f16_aligned_f16acc" #NAMELC, flash_attn_f32_f16_ ## NAMELC ## _f16acc ## SUFFIX ## _len,  flash_attn_f32_f16_ ## NAMELC ## _f16acc ## SUFFIX ## _data,  "main", 6, sizeof(vk_flash_attn_push_constants), fa_wg_denoms(FAPATH, HSK,HSV,0,TYPE,small_rows,small_cache), fa_spec_constants(FAPATH, HSK,HSV,0,TYPE,small_rows,small_cache), fa_align(FAPATH,HSK,HSV,TYPE,small_rows,small_cache), true, true, (FAPATH==FA_COOPMAT1 ? 32 : 0));     \
                     } \
                 } else { \
                     if (f32acc) { \
-                        ggml_vk_create_pipeline(device, fa.second, "flash_attn_f32_f16_f32acc"         #NAMELC, flash_attn_f32_f16_ ## NAMELC ##            SUFFIX ## _len,  flash_attn_f32_f16_ ## NAMELC ##            SUFFIX ## _data,  "main", 6, sizeof(vk_flash_attn_push_constants), fa_wg_denoms(FAPATH, HSK,HSV,1,TYPE,small_rows), fa_spec_constants(FAPATH, HSK,HSV,1,TYPE,small_rows), 1,                                        true, true, (FAPATH==FA_COOPMAT1 ? 32 : 0));     \
+                        ggml_vk_create_pipeline(device, fa.second, "flash_attn_f32_f16_f32acc"         #NAMELC, flash_attn_f32_f16_ ## NAMELC ##            SUFFIX ## _len,  flash_attn_f32_f16_ ## NAMELC ##            SUFFIX ## _data,  "main", 6, sizeof(vk_flash_attn_push_constants), fa_wg_denoms(FAPATH, HSK,HSV,1,TYPE,small_rows,small_cache), fa_spec_constants(FAPATH, HSK,HSV,1,TYPE,small_rows,small_cache), 1,                                        true, true, (FAPATH==FA_COOPMAT1 ? 32 : 0));     \
                     } else { \
-                        ggml_vk_create_pipeline(device, fa.second, "flash_attn_f32_f16_f16acc"         #NAMELC, flash_attn_f32_f16_ ## NAMELC ## _f16acc ## SUFFIX ## _len,  flash_attn_f32_f16_ ## NAMELC ## _f16acc ## SUFFIX ## _data,  "main", 6, sizeof(vk_flash_attn_push_constants), fa_wg_denoms(FAPATH, HSK,HSV,1,TYPE,small_rows), fa_spec_constants(FAPATH, HSK,HSV,1,TYPE,small_rows), 1,                                        true, true, (FAPATH==FA_COOPMAT1 ? 32 : 0));     \
+                        ggml_vk_create_pipeline(device, fa.second, "flash_attn_f32_f16_f16acc"         #NAMELC, flash_attn_f32_f16_ ## NAMELC ## _f16acc ## SUFFIX ## _len,  flash_attn_f32_f16_ ## NAMELC ## _f16acc ## SUFFIX ## _data,  "main", 6, sizeof(vk_flash_attn_push_constants), fa_wg_denoms(FAPATH, HSK,HSV,1,TYPE,small_rows,small_cache), fa_spec_constants(FAPATH, HSK,HSV,1,TYPE,small_rows,small_cache), 1,                                        true, true, (FAPATH==FA_COOPMAT1 ? 32 : 0));     \
                     } \
                 } \
             } \
@@ -8008,11 +8008,11 @@ static void ggml_vk_mul_mat_id(ggml_backend_vk_context * ctx, vk_context& subctx
     }
 }
 
-static bool ggml_vk_flash_attn_scalar_shmem_support(const vk_device& device, const uint32_t hsk, uint32_t hsv) {
+static bool ggml_vk_flash_attn_scalar_shmem_support(const vk_device& device, const uint32_t hsk, uint32_t hsv, bool small_cache) {
     // Needs to be kept up to date on shader changes
     GGML_UNUSED(hsv);
     const uint32_t wg_size = scalar_flash_attention_workgroup_size;
-    const uint32_t Br = get_fa_scalar_num_large_rows(hsk, hsv);
+    const uint32_t Br = get_fa_scalar_num_large_rows(hsk, hsv, small_cache);
     const uint32_t Bc = scalar_flash_attention_Bc;
 
     const uint32_t tmpsh = wg_size * sizeof(float);
@@ -8136,6 +8136,8 @@ static void ggml_vk_flash_attn(ggml_backend_vk_context * ctx, vk_context& subctx
     uint32_t workgroups_y = (uint32_t)neq2;
     uint32_t workgroups_z = (uint32_t)neq3;
 
+    const bool small_cache = nek1 < 1024;
+
     // For scalar/coopmat1 FA, we can use the "large" size to accommodate qga.
     // For coopmat2 FA, we always use the small size (which is still pretty large for gqa).
     uint32_t max_gqa;
@@ -8143,7 +8145,7 @@ static void ggml_vk_flash_attn(ggml_backend_vk_context * ctx, vk_context& subctx
     case FA_SCALAR:
     case FA_COOPMAT1:
         // We may switch from coopmat1 to scalar, so use the scalar limit for both
-        max_gqa = get_fa_scalar_num_large_rows(HSK, HSV);
+        max_gqa = get_fa_scalar_num_large_rows(HSK, HSV, small_cache);
         break;
     case FA_COOPMAT2:
         max_gqa = get_fa_num_small_rows(FA_COOPMAT2);
@@ -8177,7 +8179,7 @@ static void ggml_vk_flash_attn(ggml_backend_vk_context * ctx, vk_context& subctx
 
     // with large hsk/hsv, scalar path may need to use small_rows to fit in shared memory
     if (path == FA_SCALAR &&
-        !ggml_vk_flash_attn_scalar_shmem_support(ctx->device, HSK, HSV)) {
+        !ggml_vk_flash_attn_scalar_shmem_support(ctx->device, HSK, HSV, small_cache)) {
         small_rows = true;
     }
 
@@ -8193,7 +8195,7 @@ static void ggml_vk_flash_attn(ggml_backend_vk_context * ctx, vk_context& subctx
         v_stride /= 4;
     }
 
-    uint32_t alignment = fa_align(path, HSK, HSV, k->type, small_rows);
+    uint32_t alignment = fa_align(path, HSK, HSV, k->type, small_rows, small_cache);
     bool aligned = (KV % alignment) == 0 &&
                    // the "aligned" shader variant will forcibly align strides, for performance
                    (q_stride & 7) == 0 && (k_stride & 7) == 0 && (v_stride & 7) == 0;
@@ -8205,7 +8207,7 @@ static void ggml_vk_flash_attn(ggml_backend_vk_context * ctx, vk_context& subctx
 
     bool f32acc = path == FA_SCALAR || dst->op_params[3] == GGML_PREC_F32;
 
-    vk_fa_pipeline_state fa_pipeline_state(HSK, HSV, small_rows, path, aligned, f32acc);
+    vk_fa_pipeline_state fa_pipeline_state(HSK, HSV, small_rows, small_cache, path, aligned, f32acc);
 
     vk_pipeline pipeline = nullptr;